Crystalline polypropylene is excellent in mechanical properties and chemical resistance and is economical so that it is employed for a variety of moldings. However, when a homopolymer of propylene is used as the crystalline polypropylene, the homopolymer is high in rigidity but is inferior in flexibility and low temperature impact-strength. For this reason, a method for combining homopolymer of propylene with an ethylene-propylene elastomer or an ethylene-propylene-diene elastomer and a process for producing so-called block copolymers by homopolymerization of propylene followed by copolymerization of propylene with ethylene has been disclosed.
In recent years, a process for producing isotactic polypropylene by polymerizing propylene with the aid of a new catalyst different from the conventional catalyst system has been disclosed, the new catalyst being comprised of a metallocene and an aluminoxane. Homopolymerization of propylene with the aid of a similar catalyst followed by copolymerization of propylene with ethylene to form the so-called block copolymer is also known.
For instance, use of dimethylsilyl-bis(2,4-dimethylcyclopentadienyl)zirconium dichloride as metallocene is taught in Japanese Laid-open Patent Appln. No. Hei. 4-337308. An example of employing dimethylsilyl-bis(methylcyclopentadienyl)hafnium dichloride is taught in Japanese Laid-open Patent Appln. No. Hei. 6-28757. An example of using rac-ethylene-bis-indenyl hafnium dichloride, rac-dimethylsilyl-bis-indenyl hafnium dichloride, and rac-phenylmethylsilyl-bis-indenyl hafnium dichloride is taught in Japanese Laid-open Patent Appln. No. Hei. 5-202152 and Japanese Laid-open Patent Appln. No. Hei. 6-206921. An example of using dimethylsilylene-bis(2-methylindenyl)zirconium dichloride and dimethylsilylene-bis(tetrahydroindenyl)zirconium is taught in Japanese Laid-open Patent Appln. No. Hei. 6-172414.
It is the current status that moldings made of generally known propylene-ethylene block copolymers obtained by using these metallocenes are improved in flexibility and low temperature impact-resistance to a certain degree but are inferior in heat resistance and rigidity and their intended use is limited in this aspect. In addition, transparency of the moldings is extremely deteriorated so that the intended use is also limited.
Accordingly, it is an object of the present invention to provide industrially advantageous polypropylene having an excellent balance of physical properties such as impact-resistance, especially at a low temperature, rigidity, heat resistance and transparency.
As a result of extensive researches carried out to achieve the aforesaid object, the present inventors have now found a polypropylene composition comprised predominantly of polypropylene having a specific structure and a propylene-.alpha.-olefin copolymer and moldings manufactured therefrom having an excellent balance of physical properties, i.e., extremely good impact-strength, especially at a low temperature, rigidity, heat resistance, and transparency. The present invention has been accomplished on the basis of the above finding.
According to the present invention, there is provided a polypropylene composition comprised of 20-95% by weight of polypropylene defined in the following
[I] and 5-80% by weight of a propylene-.alpha.-olefin copolymer defined in the following [II]: PA1 [I] polypropylene featured by having: PA1 [II] a propylene-.alpha.-olefin copolymer containing 10-90% by weight of a constituent derived from propylene and 10-90% by weight of a constituent derived from .alpha.-olefin other than propylene. PA1 the compound (B): an aluminoxane, PA1 the compound (C): a finely particulate carrier, and PA1 the compound (D): an organoaluminum compound. PA1 The compound (B): an aluminoxane, PA1 The compound (C): a finely particulate carrier, and The PA1 compound (D): an organoaluminum compound. PA1 (1) A method wherein a trialkylaluminum is reacted directly with water, using an organic solvent such as toluene or ether, PA1 (2) A method wherein a trialkylaluminum is reacted with a salt containing water of crystallization, for example, cupric sulfate hydrate, aluminum sulfate hydrate, etc., PA1 (3) A method wherein a trialkylaluminum is reacted with silica gel impregnated with water, PA1 (4) A method wherein trimethylaluminum is mixed with triisobutylaluminum and the mixture is reacted directly with water, using an organic solvent such as toluene or ether, PA1 (5) A method wherein trimethylaluminum is mixed with triisobutylaluminum and the mixture is reacted with a salt containing water of crystallization, for example, cupric sulfate hydrate or aluminum sulfate hydrate, and PA1 (6) A method wherein silica gel or the like is impregnated with water, then reacted with triisobutylaluminum, and thereafter with trimethylaluminum.
(1) a ratio of isotactic pentad (mmmm) of 0.900-0.949, PA2 (2) the 2,1- and 1,3-propylene units in the polymer chain in the amount of 0-1 mole %, PA2 (3) a weight average molecular weight (Mw) of 40,000-1,000,000, PA2 (4) a ratio of a weight average molecular weight (Mw) to a number average molecular weight (Mn), i.e., (Mw)/(Mn), of 1.5-3.8, and PA2 (5) in case of elevating the temperature of o-dichlorobenzene continuously or stepwise up to given temperatures to measure the amount of eluted polypropylene at each temperature, the position of a main elution peak is 95-110.degree. C. and the amount of components existing in the range of .+-.10.degree. C. of the main elution peak is at least 90% of the total amounts of components eluted at a temperature higher than 0.degree. C., and
In accordance with the present invention, there is also provided the aforesaid polypropylene composition wherein the polypropylene [I] defined in (5) is as follows: in case of elevating the temperature of o-dichlorobenzene continuously or stepwise up to given temperatures to measure the amount of eluted polypropylene at each temperature, the position of a main elution peak is 95-110.degree. C. and the amount of components (E.+-.10) existing in the range of .+-.10.degree. C. of the main elution peak is at least 95% of the total amounts of components eluted at a temperature higher than 0.degree. C.
According to the present invention, there is further provided the aforesaid polypropylene composition wherein a melting point (Tm) of the aforesaid polypropylene [I] is 147-160.degree. C.
According to the present invention, there is still further provided the aforesaid polypropylene composition wherein an .alpha.-olefin in the propylene-.alpha.-olefin copolymer [II] is ethylene and (a) a weight average molecular weight (Mw) is 30,000-1,000,000, (b) a ratio of a weight average molecular weight (Mw) to a number average molecular weight (Mn), i.e. (Mw)/(Mn) is 1.5-3.8, and (c) in case of elevating the temperature of o-dichlorobenzene continuously or stepwise, an amount eluted below 0.degree. C. [E(R)] is at least 80% by weight of the total eluted amount.
According to the present invention, there is still further provided the aforesaid polypropylene composition wherein in .beta.' dispersion measured by a dynamic viscoelasticity measuring apparatus a temperature showing the maximum value of tan-.delta. being -65.degree. C. to -40.degree. C., and a half-width of the peak temperature [T.beta.'(1/2)] is below 20.degree. C.
According to the present invention, there is still further provided the aforesaid polypropylene composition wherein the .alpha.-olefin in the propylene-.alpha.-olefin copolymer [II] is ethylene, (a) a weight average molecular weight (Mw) is 30,000-1,000,000, (b) a ratio of a weight average molecular weight (Mw) to a number average molecular weight (Mn), i.e. (Mw)/(Mn) is 1.5-3.8, (c) in case of elevating the temperature of o-dichlorobenzene continuously or stepwise, an amount eluted above 0.degree. C. [E(E)] is at least 50% by weight of the total eluted amount.
According to the present invention, there is still further provided the aforesaid polypropylene composition wherein E(E) is at least 80% by weight of the total eluted amount.
According to the present invention, there is still further provided the aforesaid polypropylene composition wherein in a .beta.'-dispersion measured in a dynamic viscoelasticity measuring apparatus, a temperature (T.beta.') showing the maximum value of tan-.delta. is within the range of higher than -40.degree. C. and not higher than -1.degree. C.
According to the present invention, there is still further provided the aforesaid polypropylene composition wherein the polypropylene [I] and the propylene-.alpha.-olefin copolymer [II] have been produced by the aid of a catalyst system comprised predominantly of the compounds (A), (B), (C), and (D) shown below: the compound (A): a transition metal compound of the following general formula: EQU Q(C.sub.5 H.sub.4-m R.sup.1.sub.m)(C.sub.5 H.sub.4-n R.sup.2.sub.n)MXY
wherein (C.sub.5 H.sub.4-m R.sup.1.sub.m) and (C.sub.5 H.sub.4-n R.sup.2.sub.n) each stand for a substituted cyclopentadienyl group, m and n each stands for an integer of 1-3, R.sup.1 and R.sup.2 may be the same or different and each stands for a hydrocarbon group with 1-20 carbon atoms, a silicon-containing hydrocarbon group, with the proviso that the site of R.sup.1 and R.sup.2 on the cyclopentadienyl rings should take a configuration where any symmnetrical plane containing M is absent and that R.sup.1 or R.sup.2 is existent in at least one carbon atom adjacent to the carbon atom connected to Q in at least one cyclopentadienyl ring, Q stands for a bivalent hydrocarbon radical, unsubstituted silylene radical or a hydrocarbon-substituted silylene radical bridging the groups (C.sub.5 H.sub.4-m R.sup.1.sub.m) and (C.sub.5 H.sub.4-n R.sup.2.sub.n), M stands for a transition metal Ti, Zr or Hf, and X and Y may be the same or different and each stands for a hydrogen atom, a halogen atom or a hydrocarbon group,
According to the present invention, there is still further provided the aforesaid polypropylene composition wherein the compound (A) is dimethylsilylene(2,3,5-trimethylcyclopentadienyl) (2',4',5'-trimethylcyclopentadienyl)zirconium dichloride.
According to the present invention, there is still further provided the aforesaid polypropylene composition which has been obtained by polymerization of the polypropylene [I] followed by copolymerization of the propylene-.alpha.-olefin [II].